In recent years, inhibitors of HIV reverse transcriptase (RT) have become an important class of therapeutic agents for inhibition and treatment of HIV infection in humans. Compounds that inhibit the enzymatic functions of HIV reverse transcriptase inhibit replication of HIV in infected cells. Such compounds are useful in the prevention or treatment of HIV infection in humans, as demonstrated by known RT inhibitors such as zidovudine, didanosine, zalcitabine, stavudine, lamivudine, emtricitabine, abacavir, tenofovir, nevirapine, delavirdine and efavirenz, the main drugs thus far approved for use in the treatment of AIDS.
As with any antiviral therapy, use of RT inhibitors in the treatment of AIDS eventually leads to a virus that is less sensitive to the given drug. Resistance (reduced sensitivity) to these drugs is the result of mutations that occur in the reverse transcriptase segment of the pol gene. Several mutant strains of HIV have been characterized, and resistance to known therapeutic agents is believed to be due to mutations in the RT gene. Thus, to be effective, new HIV RT inhibitors must be effective not only against wild-type strains of HIV, but must also demonstrate efficacy against the newly emerging mutant strains that are resistant to the commercially available RT inhibitors. Accordingly, there continues to be a need for new HIV RT inhibitors, for example, those targeting the HIV RT in both wild type and mutant strains of HIV.